Method and apparatus for feature configuration in remotely located ultrasound imaging system

ABSTRACT

A method and apparatus for configuring an ultrasound imaging system at a remote location by obtaining an encrypted feature key from a central location (e.g., via telephone) and then inputting that feature key into the ultrasound imaging system using an operator interface (e.g., a keyboard). To validate the feature key, the ultrasound imaging system decrypts the encrypted data and then compares the decrypted data to validation data pre-stored in the system. If the decrypted data matches the validation data, then the optional feature identified by the feature key will be enabled each time the system is booted or initialized. Optionally, an expiration date can be associated with the activated option, after which date the feature will be disabled when the system is initialized. Similarly, an activated optional feature can be disabled at a remote location by the input of an encrypted key obtained from a central location.

RELATED APPLICATION

This is a divisional of and claims priority from U.S. patent applicationSer. No. 09/065,171 filed on Apr. 23, 1998. Now U.S. Pat. No. 6,246,770issue date Jun. 12, 2001.

FIELD OF THE INVENTION

This invention generally relates to systems for ultrasound imaging ofthe human anatomy for the purpose of medical diagnosis. In particular,the invention relates to a method for configuring a remotely locatedultrasound imaging system to add or delete features.

BACKGROUND OF THE INVENTION

Conventional ultrasound scanners create two-dimensional B-mode images oftissue in which the brightness of a pixel is based on the intensity ofthe echo return. The basic signal processing chain in the conventional Bmode is depicted in FIG. 1. An ultrasound transducer array 2 isactivated to transmit an acoustic burst along a scan line. The return RFsignals are detected by the transducer elements and then formed into areceive beam by the beamformer 4. The beamformer output data (I/Q or RF)for each scan line is passed through a B-mode processing chain 6 whichincludes demodulation, equalization filtering, envelope detection andlogarithmic compression. Depending on the scan geometry, up to a fewhundred vectors may be used to form a single acoustic image frame. Tosmooth the temporal transition from one acoustic frame to the next, someacoustic frame averaging 8 may be performed before scan conversion.

In general, the log-compressed display data is converted by the scanconverter 10 into X-Y format for video display. On some systems, frameaveraging may be performed on the X-Y data (indicated by dashed block12) rather than the acoustic frames before scan conversion, andsometimes duplicate video frames may be inserted between acoustic framesin order to achieve a given video display frame rate. The scan-convertedframes are passed to a video processor 14, which maps the video data toa gray-scale mapping for video display. The gray-scale image frames arethen sent to a video monitor 18 for display.

System control is centered in a host computer 20, which accepts operatorinputs through an operator interface 22 (e.g., a keyboard) and in turncontrols the various subsystems. (In FIG. 1, only the image datatransfer paths are depicted.) During B-mode imaging, a long sequence ofthe most recent images are stored and continuously updated automaticallyin a cine memory 16. Some systems are designed to save the R-θ acousticimages (this data path is indicated by the dashed line in FIG. 1), whileother systems store the X-Y video images. The image loop stored in cinememory 16 can be reviewed via track-ball control, and a section of theimage loop can be selected for hard disk storage.

For an ultrasound imaging system which has been configured with afree-hand three-dimensional imaging capability, the selected imagesequence stored in cine memory 16 is transferred to the host computer 20for three-dimensional reconstruction. The result is written back intoanother portion of the cine memory, from where it is sent to the displaysystem 18 via video processor 14.

From the standpoint of the vendor of the ultrasound imaging system, itis desirable to sell or lease systems having built-in optional featureswhich can be activated at a location remote from a central billingstation. For example, the capability of free-hand three-dimensionalimaging can be an optional feature which must be purchased from thesystem vendor. To ensure that the system user is charged for the use ofsuch optional features, it is known to provide means for blockingactivation of optional features unless authorization is obtained fromthe manufacturer. Authorization can also be given to allow for use of anoptional feature free of charge for a predetermined trial period. In oneconventional ultrasound system, this is accomplished by delivery of anauthorized feature activation disk, which is inserted into a slot in thesystem. The disk has validation information and feature informationstored thereon. The system compares the validation information with aunique validation standard pre-stored in the system memory. If thevalidation data matches the unique pre-stored standard, the featureinformation stored on the disk is incorporated in the systemconfiguration database. Thereafter and until the expiration date,whenever the system is initialized, optional feature or featuresrepresented by the feature information of the disk will be enabled.

However, there is a need for a method of configuring an ultrasoundimaging system at a remote location without physically transferring anauthorization disk or card from the central location to the remotelocation. In particular, there is a need for a method of systemconfiguration which can be carried out remotely while avoiding thedelays inherent in the shipment or delivery of a disk or card from acentral location.

SUMMARY OF THE INVENTION

The present invention is a method and apparatus for configuring anultrasound imaging system at a remote location by obtaining an encryptedfeature key from a central location (e.g., via telephone) and theninputting that feature key into the ultrasound imaging system using anoperator interface (e.g., a keyboard). To validate the feature key, thesystem decrypts the encrypted data and then compares the decrypted datato validation data pre-stored in the system. If the decrypted datamatches the validation data, then the optional feature identified by thefeature key will be enabled each time the system is booted orinitialized. Optionally, an expiration date can be associated with theactivated option, after which date the feature will be disabled when thesystem is initialized.

In accordance with the broad scope of the invention, an activatedoptional feature can be disabled at a remote location by the input of anencrypted key obtained from a central location. The term “feature key”shall be used hereinafter to mean any key for activating or deactivatingan optional feature.

To enable an optional feature on the ultrasound system in accordancewith the preferred embodiment of the invention, an authorized servicerepresentative or other user at the remote location opens acommunication link with a central location. In order to obtain a featurekey for enabling the feature, the user must identify the option desiredand provide the machine identification number and the option expirationdate to the central location. Service personnel at the central locationthen run a key maker application using the given data. The key makerapplication employs a value extractor to organize the inputted data intovectors, and an encryption engine to transform those vectors (bymultiplying each vector with a non-singular matrix) into an encryptedfeature key comprising a string of numeric characters. The encryptedfeature key is then communicated to the user at the remote location.

To facilitate entry of the encrypted feature activation key into thesystem, first the user must enter a predetermined sequence ofalphanumeric characters representing an enter key entry mode command.The characters can be entered, for example, by depressing keys locatedeither on a front panel of the system or on a modular keyboard connectedto the system. The enter key entry mode command places the machine in asuspended state (i.e., the feature key entry mode) in which the nextdata inputted into the system is processed as a feature key. The userthen enters the string of numeric characters representing the encryptedfeature key into the system.

The ultrasound imaging system at the remote location is programmed withan encryption engine identical to that used at the central location togenerate the encrypted feature key. After reading the encrypted featurekey (i.e., storing the inputted numeric characters in a buffer), thesystem extracts the values representing the key identifier, machineidentification number, option and option expiration date. The extractedvalues are then organized into vectors, which vectors are input into theencryption engine. The encryption engine de-crypts the encrypted featurekey by linear transformation of the inputted vectors using the matrixwhich results when the non-singular matrix used during the encryptionprocess is inverted. The decrypted vectors representing the keyidentifier and machine identification number are then validated. If thekey identifier and machine identification number are both valid, thenthe decrypted option and expiration date vectors are input to an optionactivator, which copies the option and expiration date data into theoptions structure within the system configuration database. If theexpiration date is valid, the feature identified by the installed optiondata will be activated each time that the system is booted, until theexpiration date.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the major functional subsystems withina conventional real-time ultrasound imaging system.

FIG. 2 is a block diagram showing a system for configuring an ultrasoundimaging system at a remote location by obtaining an encrypted featurekey from a central location via a communications link in accordance withone preferred embodiment of the invention.

FIG. 3 is a flowchart showing the steps of a method for configuring anultrasound imaging system in accordance with the preferred embodiment ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 depicts the overall system for feature configuration of anultrasound imaging system at a remote location 24 using an encryptedfeature key transmitted from a central location 26. Although FIG. 2shows only the host computer 20 and the operator interface 22 of theultrasound imaging system, it will be appreciated that the ultrasoundimaging system at remote location 24 may also incorporate the componentsdepicted in FIG. 1 or components of a different type of ultrasoundimaging system.

The remote location 24 is also provided with a communications module 28which can be connected to a communications module 30 at the centrallocation 26 by opening a communications link 29. For example, thecommunications link can be a telephone line. In accordance with thepreferred embodiment of the invention, to enable an optional feature onthe ultrasound imaging system, a user at the remote location 24 mustobtain an encrypted feature key from the central location. To accomplishthis, the user must first open communications link 29 and then transmitnumeric data representing the option to be activated, the expirationdate of that option and a machine identification number (i.e., serialnumber) which is unique to the system being configured.

After this information has been transmitted, service personnel at thecentral location input the transmitted data into an operator interface32 which interfaces with a central computer 35. The data is input intothe operator interface as a string of numeric characters. The output ofoperator interface 32 is input to a value extractor 34 which isincorporated in central computer 35. Initially, the string of numericcharacters is stored in a buffer incorporated in the value extractor 34.The central computer also adds a key identifier to the string of numericcharacters. The key identifier is a special code used to identify avalid feature key. Optionally, a limit can be placed on the duration ofoption activation as represented by the expiration date, e.g., thecentral computer may be programmed to reject any request for a featureactivation key made more than 30 days prior to the expiration date. Thevalue extractor 34 then organizes the string of numeric characters intoa series of vectors in R^(x) space, where x is the dimension of anon-singular matrix used in the encryption process.

The central computer 35 further comprises an encryption engine 36 whichreceives the series of vectors output by the value extractor 34. Toencrypt these vectors, the encryption engine 36 utilizes a non-singularencryption matrix A. The matrix A is non-singular to allow fordecryption using the inverted matrix A⁻¹. In accordance with thepreferred embodiment of the invention, the non-singular encryptionmatrix is not pre-stored, but rather is generated by the centralcomputer from pre-stored matrix precursor data. As a result, theencryption matrix cannot be simply addressed and read out of memory bypersons having access to the central computer, thus providing an addedmeasure of security.

After the encryption matrix A has been generated, each vector V_(i) isencrypted by performing the linear transformation L(V_(i))=AV_(i). Theresulting encrypted vectors form a string of numeric characters whichconstitute the encrypted feature key. The service personnel at thecentral location 26 then transmit the encrypted feature key to theremote location 24 via the communications link 29 or via a differentcommunications link.

Upon receipt of the encrypted feature key, the user at the remotelocation places the ultrasound imaging system in a feature key entrymode and then inputs the encrypted feature key into the host computer 20via the operator interface 22. The encrypted key is stored in a bufferincorporated in the value extractor 38. The value extractor 38 parsesthe string of numeric characters constituting the encrypted key into therespective values: key identifier, machine identification number, optionand expiration date, and then organizes those values into respectiveencrypted vectors X_(i). The encrypted vectors are then decrypted by anencryption engine 40 using matrix A⁻¹, i.e., the inverted non-singularencryption matrix. For added security, the host computer 20 constructsmatrix A⁻¹ from pre-stored precursor data. Each encrypted vector X_(i)is decrypted by performing the linear transformation L(X_(i))=A⁻¹X_(i).The decrypted key identifier and machine identification number areoutput to a key validator 42. If the key validator determines that boththe key identifier and the machine identification number are valid, thenthe key validator generates a signal which enables the option activator44. The option activator 44 receives the decrypted option and expirationdate from the encryption engine 40 and copies that data into respectivefields in options data structure 46, which forms part of the systemconfiguration database. The ultrasound imaging system is then rebootedautomatically. Upon rebooting, the options handler 48 configures thesystem in accordance with the new data stored in the options datastructure 46. In particular, the options handler 48 enables the featureidentified by the new options datum stored in the options field. Thatfeature will be enabled each time the system is initialized untilexpiration of the option on the date indicated in the expiration datefield of the options data structure.

The method for configuring a remotely located ultrasound imaging systemin accordance with the preferred embodiment of the invention is shown inmore detail in FIG. 3. To facilitate entry of the encrypted feature keyinto the system, first the user must enter a predetermined sequence ofalphanumeric characters representing an enter key entry mode command(step 50). The characters can be entered, for example, by depressingkeys located either on a front panel of the system or on a modularkeyboard connected to the system. A parameter routine interprets thepredetermined sequence of alphanumeric characters (e.g., the sequenceΔ+2) as the enter key entry mode command, placing the machine in asuspended state (i.e., the feature key entry mode). In the feature keyentry mode, the next data inputted into the system will be processed asa feature key.

In the feature key entry mode, the user enters the string of numericcharacters representing the encrypted feature key into the operatorinterface (step 52). Optionally, as the user types in the encryptedfeature key, the system can respond to each key depression with a formof acknowledgement. The end of the string of numeric characters isindicated by depressing the “Enter” on the operator interface. Theinputted encrypted key is then read (step 54) by storing the string ofnumeric characters in a buffer incorporated in the value extractor 38(see FIG. 2). The “Read Key” function is enabled when the user types inthe enter key entry mode command.

The value extractor parses or extracts the values (step 56) representingthe key identifier, machine identification number, option and expirationdate and then organizes those values into respective encrypted vectors.The encrypted vectors are then decrypted (step 58) using the invertednon-singular encryption matrix, as previously described. The decryptedkey identifier data is then compared with a key identifier pre-stored inthe system configuration database to determine whether the feature keyis valid (step 60). If the feature key is valid, then the machineidentification number, i.e., serial number, is compared with a machineidentification number (also pre-stored in the system configurationdatabase) which is unique to the system being configured (step 62). Ifthe machine identification number is valid, then the decrypted optionand expiration date are copied into respective fields in an options datastructure in the system configuration database (step 70). The ultrasoundimaging system is then rebooted automatically (step 72).

If either the key identifier or the machine identification number isinvalid (steps 60 and 62 in FIG. 3), then the system exits the featurekey entry mode (step 64). The message “Invalid Key” is displayed on themonitor (step 66). Then the system returns to its previous state withoutrebooting (step 68).

The foregoing preferred embodiments have been disclosed for the purposeof illustration. Variations and modifications of the basic concept ofthe invention will be readily apparent to persons skilled in the art. Inparticular, it will be appreciated that the encrypted feature key can betransmitted from the central location to a remote location via acommunications link different than the link used to transmit data fromthe remote location to the central location. In addition, although thedisclosed preferred embodiments employ encrypted numeric codes, it willbe appreciated that the system can be readily adapted to operate usingencrypted alphabetic or alphanumeric codes. All such variations andmodifications are intended to be encompassed by the claims set forthhereinafter.

What is claim is:
 1. A method for configuring a computerized system at aremote location, comprising the steps of: storing a validationidentifier inside said system; transmitting an option identifier whichidentifies a change in system configuration from said remote location toa central location; encrypting said validation identifier and saidoption identifier at said central location; transmitting an encryptedfeature key comprising a sequence of characters from said centrallocation to said remote location, said encrypted feature key comprisingsaid encrypted validation identifier and said encrypted optionidentifier; placing said system in a feature key entry mode; inputtingsaid encrypted feature key into said system by operation of a sequenceof input keys corresponding to said sequence of characters of saidencrypted feature key; decrypting said encrypted feature key inside saidsystem to form decrypted data comprising a decrypted validationidentifier and a decrypted option identifier; comparing said decryptedvalidation identifier with said stored validation identifier; altering asystem configuration database inside said system to reflect said changein system configuration if said decrypted validation identifier matchessaid stored validation identifier.
 2. The method as defined in claim 1,wherein said change in system configuration is addition of an optionalfeature.
 3. The method as defined in claim 1, wherein said change insystem configuration is deletion of an optional feature.
 4. A method forconfiguring a computerized system, comprising the steps of: booting asystem with an intial system configuration; placing said system in afeature key entry mode; inputting an encrypted feature key into saidsystem via an operator interface, said encrypted feature key comprisingan encrypted validation identifier and an encrypted option identifier;decrypted said encrypted feature key inside said system to fromdecrypted date comprising a decrypted validation identifier and adecrypted option identifier; comparing said decrypted validationidentifier with a pre-stored validation identifier; altering a systemconfiguration database inside said system to reflect a change in systemconfiguration identifier by said decrypted option identifier if saiddecrypted validation identifier matches said stored validationidentifier; and rebooting said system with said change systemconfiguration following said altering step and before use of saidsystem.
 5. The method as defined in claim 4, wherein said change insystem configuration is addition of an optional feature.
 6. The methodas defined in claim 4, wherein said change in system configuration isdeletion of an optional feature.
 7. An ultrasound imaging systemcomprising: an ultrasound transmitter for transmitting ultrasound energyinto a volume of ultrasound scatterers; a signal processing chain foracquiring display data representing an image of ultrasound scatterers insaid volume in accordance with a system configuration comprising enabledfeatures, said display data being based on ultrasound energy scatteredby said ultrasound scatterers; a monitor for displaying said image inresponse to receipt of said display data; a memory for storing a systemconfiguration database representing said enabled features of said systemconfiguration; an operator interface comprising a plurality of keys forinputting data into said system; means for placing said system in afeature key entry mode in response to a predetermined command input viasaid operator interface; and decrypting means for outputting decrypteddata in response to depression of a sequence of keys of said operatorrepresenting an encrypted feature key comprising an encrypted validationidentifier and an encrypted option identifier, said decrypted datacomprising a decrypted validation identifier and a decrypted optionidentifier; validating means for determining if said decryptedvalidation identifier is valid; and means for altering said systemconfiguration as a function of said decrypted option identifier only ifsaid decrypted validation identifier is valid.
 8. The system as definedin claim 7, wherein said change in system configuration is addition ofan optional feature.
 9. The system as defined in claim 7, wherein saidchange in system configuration is deletion of an optional feature. 10.The system as defined in claim 7, further comprising means for storingdecryption matrix precursor data and means for constructing a decryptionmatrix based on said decryption matrix precursor data, wherein saiddecrypting means perform decryption by applying said decryption matrixto vectors formed from said encrypted feature key.
 11. A systemcomprising: an operation interface; memory which stores a computerbooting routine, an optional computer feature, a system configurationdatabase comprising a validation identifier and a list of computerfeatures to be activated at during computer booting, and a computerfeature activation/de-activation routine for selectively adding ordeleting an identifier of said optional computer feature to or from saidlist of activated computer features in said system configurationdatabase; and a computer which executes said computer booting routineduring booting, executes said computer feature activation/de-activationroutine only in response to entry of a first predetermined command viasaid operator interface after booting, and executes said computeroptional feature in response to entry of a second predetermined commandvia said operator interface after booting if said optional computerfeature has been activated during booting, wherein said computer featureactivation/de-activation routine comprises the following steps:decrypting a feature key entered via said operator interface to formdecrypted data comprising a decrypted validation identifier and adecrypted optional computer feature identifier; comparing said decryptedvalidation identifier with said stored validation identifier in saidsystem configuration database; and adding or deleting said decryptedoptional computer feature identifier to or from said list of activatedcomputer features in said system configuration database provided thatsaid decrypted validation identifier matches said stored validationidentifier.
 12. The system as recited in claim 11, wherein said systemis a scanner.
 13. The system as recited in claim 12, wherein saidscanner is an ultrasound imaging system.
 14. The system as recited inclaim 11, wherein said computer feature activation/de-activation routinefurther comprises the step of rebooting said computer following saidadding/deleting step and before use of said system.
 15. The system asrecited in claim 11, wherein said decrypted data derived from saidfeature key further comprises a decrypted expiration date, and saidadding step further comprises associating said decrypted expiration datewith said decrypted optional computer feature identifier in said list ofactivated computer features in said system configuration database. 16.The system as recited in claim 11, wherein said computer featureactivation/de-activation routine further comprises the step ofconstructing a decryption matrix inside said system from decryptionmatrix precursor data, wherein said decrypting step is carried out byapplying said decryption matrix to vectors formed from said feature key.17. The system as recited in claim 11, wherein said validationidentifier comprises a system identifier which uniquely identifies saidsystem.
 18. The system as recited in claim 17, wherein said validationidentifier further comprises a key identifier.
 19. A method forconfiguring a computerized system, comprising the following steps:booting said computerized system with a system configuration whereinonly those optional computer features which are identified in a list ofactivated optional computer features listed in a system configurationdatabase stored in system memory are activated; inputting a command viaan operator interface which causes said computerized system to enter afeature activation mode; inputting an encrypted feature key into saidcomputerized system via said operator interface while said computerizedsystem is in said feature activation mode, said encrypted feature keycomprising an encrypted validation identifier and an encrypted optionalcomputer feature identifier, wherein said encrypted optional computerfeature identifier corresponds to an optional computer feature notidentified in said list of activated optional computer features;automatically decrypting said feature key inputted via said operatorinterface to form decrypted data comprising a decrypted validationidentifier and a decrypted optional computer feature identifier;automatically comparing said decrypted validation identifier with astored validation identifier in said system configuration database; andautomatically adding said decrypted optional computer feature identifierto said list of activated computer features in said system configurationdatabase if said decrypted validation identifier matches said storedvalidation identifier.
 20. The method as recited in claim 19, furthercomprising the step of rebooting said computer with a systemconfiguration comprising said optional computer feature following saidadding step and before use of said system.
 21. The method as recited inclaim 19, wherein said encrypted feature key further comprises anencrypted expiration date, said decrypted data derived from said featurekey further comprises a decrypted expiration date, and said adding stepfurther comprises associating said decrypted expiration date with saiddecrypted optional computer feature identifier in said list of activatedcomputer features in said system configuration database.
 22. The methodas recited in claim 19, wherein said computer feature activation routinefurther comprises the step of constructing a decryption matrix insidesaid system from decryption matrix precursor data, wherein saiddecrypting step is carried out by applying said decryption matrix tovectors formed from said feature key.
 23. The method as recited in claim19, wherein said validation identifier comprises a system identifierwhich uniquely identifies said computerized system.
 24. The method asrecited in claim 23, wherein said validation identifier furthercomprises a key identifier.
 25. A method for configuring a computerizedsystem, comprising the following steps: booting said computerized systemto have a system configuration wherein only those optional computerfeatures which are identified in a list of activated optional computerfeatures listed in a system configuration database stored in systemmemory are activated; inputting a command via an operator interfacewhich causes said computerized system to enter a feature de-activationmode; inputting an encrypted feature key into said computerized systemvia said operator interface while said computerized system is in saidfeature de-activation mode, said encrypted feature key comprising anencrypted validation identifier and an encrypted optional computerfeature identifier, wherein said encrypted optional computer featureidentifier corresponds to an optional computer feature identified insaid list of activated optional computer features; automaticallydecrypting said feature key inputted via said operator interface to formdecrypted data comprising a decrypted validation identifier and adecrypted optional computer feature identifier; automatically comparingsaid decrypted validation identifier with a stored validation identifierin said system configuration database; and automatically deleting saiddecrypted optional computer feature identifier from said list ofactivated computer features in said system configuration database ifsaid decrypted validation identifier matches said stored validationidentifier.
 26. The method as recited in claim 25, further comprisingthe step of rebooting said computer with a system configuration notincluding said optional computer feature following said deleting stepand before use of said system.
 27. A method for configuring acomputerized system, comprising the steps of: pre-storing an option andan activation status datum in said system, said activation status datumhaving a first value indicating that said option should not be activatedwhen said system is booted; transmitting data comprising an optionidentifier identifying said option and a machine identification numberidentifying said system from a remote location to a central location; atsaid central location, receiving said data, adding a key identifier tosaid data, encrypting said key identifier and said data to form anencrypted feature key, and transmitting said encrypted feature key tosaid remote location; inputting said encrypted feature key into saidsystem via an operator interface; inside said system, automaticallyperforming the following steps: decrypting said encrypted feature keyinside said system to form decrypted data comprising said keyidentifier, said option identifier and said machine identificationnumber; validating said key identifier and said machine identificationnumber resulting from decryption; and changing said activation statusdatum from said first value to a second value if said key identifier andsaid machine identification number are valid, said second valueindicating that said option should be activated when said system isbooted.
 28. A method for configuring a computerized system, comprisingthe steps of: pre-storing an option and an activation status datum insaid system, said activation status datum having a first valueindicating that said option should be activated when said system isbooted; transmitting data comprising an option identifier identifyingsaid option and a machine identification number identifying said systemfrom a remote location to a central location; at said central location,receiving said data, adding a key identifier to said data, encryptingsaid key identifier and said data to form an encrypted feature key, andtransmitting said encrypted feature key to said remote location;inputting said encrypted feature key into said system via an operatorinterface; and inside said system, automatically performing thefollowing steps: decrypting said encrypted feature key to form decrypteddata comprising said key identifier, said option identifier and saidmachine identification number; validating said key identifier and saidmachine identification number resulting from decryption; and changingsaid activation status datum from said first value to a second value ifsaid key identifier and said machine identification number are valid,said second value indicating that said option should not be activatedwhen said system is booted.
 29. A system comprising: an operatorinterface; memory storing an option, an option identifier identifyingsaid option, and an activation status datum, said activation statusdatum having either first or second values, said first value indicatingthat said option should not be activated when said system is booted andsaid second value indicating that said option should be activated whensaid system is booted; and a computer programmed to perform thefollowing steps in an option activation mode: detecting entry of anencrypted feature key via said operator interface: decrypting saidencrypted feature key to form decrypted data; verifying that saiddecrypted data comprise a valid key identifier and a valid machineidentification number; and after verification, changing said activationstatus datum from one of said first and second values to the other ofsaid first and second values if said decrypted data comprise said optionidentifier.
 30. The system as recited in claim 29, wherein said systemis an ultrasound imaging system.
 31. A method for changing a state ofactivation of an optional software feature stored in a computerizedsystem via an operator interface, comprising the steps of: inputting anenter feature key entry mode command; and inputting an encrypted featurekey comprising a machine identification number identifying saidcomputerized system, an option identifier identifying said optionalsoftware feature, an expiration date on which said optional softwarefeature should be de-activated, and a key identifier.